ONE of the most commonly asked question about amphibians is ''What is the difference between a frog and a toad?'' Close Cousins Most people use the word ''frog'' to describe the members of this group with smooth skin that spend most of their time in or near water. Most use the word ''toad'' to refer to the warty, chubby ones that tend to spend more time away from water.

But these are not scientific groupings, they are just common names. Scientists usually refer to all members of this group as ''frogs''.

From Vegetarian to Carnivore Adult frogs are carnivorous. They eat almost any small animals that move - insects, earthworms, fish. But unlike other amphibians, most frogs do not start out as meat eaters. Before they undergo metamorphosis, they eat mainly algae and bacteria.

A frog's intestines ''shrink'' to as little as 15 per cent of their original length as the tadpole, or young frog, undergoes metamorphosis. The adult's shorter intestines are adapted to digest animal food rather than the plant food the frog ate when it was a tadpole.

Conspicuous Callers As many as 85 per cent of all amphibians are frogs and they are the extroverts in the group. Many frogs make their presence known with loud, distinctive calls.

Usually the males do most of the calling, by inflating one or more vocal sacs with air to create resonating chambers for their calls. Here, There and Everywhere At certain times of the year, you can hear frogs calling throughout the night almost anywhere there is standing or slow-moving fresh water. From mountains to woodlands, just about every type of habitat is home to at least one type of frog.